rails--rails/activesupport/lib/active_support/deprecation/behaviors.rb

require "active_support/notifications"

module ActiveSupport
  module Deprecation
    # Whether to print a backtrace along with the warning.
    attr_accessor :debug

    # Returns the current behavior or if one isn't set, defaults to +:stderr+
    def behavior
      @behavior ||= [DEFAULT_BEHAVIORS[:stderr]]
    end

    # Sets the behavior to the specified value. Can be a single value, array, or
    # an object that responds to +call+.
    #
    # Available behaviors:
    #
    # [+stderr+]  Log all deprecation warnings to +$stderr+.
    # [+log+]     Log all deprecation warnings to +Rails.logger+.
    # [+notify]   Use +ActiveSupport::Notifications+ to notify +deprecation.rails+.
    # [+silence+] Do nothing.
    #
    # Setting behaviors only affects deprecations that happen after boot time.
    # Deprecation warnings raised by gems are not affected by this setting because
    # they happen before Rails boots up.
    #
    #   ActiveSupport::Deprecation.behavior = :stderr
    #   ActiveSupport::Deprecation.behavior = [:stderr, :log]
    #   ActiveSupport::Deprecation.behavior = MyCustomHandler
    #   ActiveSupport::Deprecation.behavior = proc { |message, callstack|
    #     # custom stuff
    #   }
    def behavior=(behavior)
      @behavior = Array(behavior).map { |b| DEFAULT_BEHAVIORS[b] || b }
    end

    # Default warning behaviors per Rails.env.
    DEFAULT_BEHAVIORS = {
      :stderr => Proc.new { |message, callstack|
        $stderr.puts(message)
        $stderr.puts callstack.join("\n  ") if debug
      },
      :log => Proc.new { |message, callstack|
         logger =
           if defined?(Rails) && Rails.logger
             Rails.logger
           else
             require 'active_support/logger'
             ActiveSupport::Logger.new($stderr)
           end
         logger.warn message
         logger.debug callstack.join("\n  ") if debug
       },
       :notify => Proc.new { |message, callstack|
          ActiveSupport::Notifications.instrument("deprecation.rails",
          :message => message, :callstack => callstack)
       },
       :silence => Proc.new { |message, callstack| }
    }
  end
end